Diffusive nature of thermal transport in stanene

TL;DR

This study demonstrates that stanene exhibits low, anisotropic, and diffusive thermal conductivity due to anharmonic phonon interactions, with potential for thermoelectric applications.

Contribution

The paper provides a comprehensive analysis of phonon transport in stanene, revealing its diffusive nature and tunability of thermal conductivity through size and surface modifications.

Findings

Thermal conductivity along zigzag and armchair directions are 10.83 and 9.2 W/m-K.

Thermal transport in stanene is completely diffusive with a mean free path of 17 nm.

Thermal conductivity can be further reduced by size tuning and surface roughness.

Abstract

Using the phonon Boltzmann transport formalism and density functional theory based calculations, we show that stanene has a low thermal conductivity. For a sample size of 1$\times$1 $\mu$m$^{2}$ ($L\times W$), the lattice thermal conductivities along the zigzag and armchair directions are 10.83 W/m-K and 9.2 W/m-K respectively, at room temperature, indicating anisotropy in the thermal transport. The low values of thermal conductivity are due to large anharmonicity in the crystal resulting in high Gr\"{u}neisen parameters, and low group velocities. The room temperature effective phonon mean free path is found to be around 17 nm indicating that the thermal transport in stanene is completely diffusive in nature. Furthermore, our study brings out the relative importance of the contributing phonon branches and reveals that, at very low temperatures, the contribution to lattice thermal conductivity comes from the flexural acoustic (ZA) branch and at higher temperatures it is dominated by the longitudinal acoustic (LA) branch. We also show that lattice thermal conductivity of stanene can further be reduced by tuning the sample size and creating rough surfaces at the edges. Such tunability in the lattice thermal conductivity in stanene suggests its applications in thermoelectric devices.